Keystone Species Virtual Lab

Learning Outcome: To examine the effects of removing a key predator from the environment usinga virtual labPredation is one factor that can limit the growth of a population. When predation ceases, a preypopulation that is normally somewhat stable can explode, causing effects to ripple out across theentire food web. The predator doesnt need to be an apex predator in order to have this kind ofeffect on a community. In this lab activity, you will see what happens when such a keystonespecies is removed from an ecosystem.Directions: Follow the following link to the virtual lab https://www.learner.org/courses/envsci/interactives/ecology/ecology.html?initLesson=1 and click Open SimulatorPart I: Food ChainFirst you'll run a less than "real-life" scenario.Step 1: Choose only one organism from each trophic level and make sure that the food chain goes in a straightline from one trophic level to the next.This will be Herbivore A eats Plant A, Omnivore A eats Herbivore A.Step 2: Click on Plant B icon. Let Plant B survive on its own and see what happens.Step 3: Predict whether each species will survive, and whether it will increase or decrease in number, as well aswhether Plant B will survive to the end

Prediction: We predicted that Herbivore A and plant A will survive but decrease in number, for the plant B wethink that it will survive to the end.

Step 4: Click on the Run icon. The simulation will run for 100 days.Step 5: Record your results in the Data Table.Step 6: Reset and run the simulation again and record your data.Use X for "die out," for "increase in numbers," and for "decrease in numbers."(X, , or )

Plant A

Herbivore A

Omnivore A

Plant B

Simulation 1

Simulation 2

Answer the following:

1.

Was your prediction correct? How did you arrive at your prediction? What differences were therebetween your prediction and the simulation?

Our prediction are not correct at all. We thought that herbivoreA and plantA will decrease population and plantB will survive until the end so plant A really decrease their number of population but herbivoreA doesntbecause they have enough food source even though they are killed by omnivoreA. The different betweenprediction and the simulation is in fact, herbivoreA were increasing not decreasing.2.

What would happen to this imaginary ecosystem if the producers were to die out?

This ecosystem would be destroyed because there is only one food source.3.

Did any of the species increase in number? What could account for this increase? Which speciesdecreased in number and what might account for this decrease?

At the beginning, every species were decreasing and increasing. After that for a while, they were stable. Thespecies that increase their population are herbivoreA and omnivoreA. For the species that decrease theirpopulation is plantA.4.

Which populations would benefit the most from the presence of decomposers?

PlantA would benefit the most because they uptake the nutrient which the decomposer decompose the deadorganisms.

Part II: Establishing the Environment

Step 1: Reset simulation.Step 2: Click on All off icon.Step 3: Click on all the plant icons. They plants should cover up the bare ground on simulation.

Prediction: The amount of plantA will be decreased because many living things eat it. The predator willincrease population because no one eat them.Step 7: Click on the Run icon. The simulation will run for 100 days.Step 8: Record your results in the Data Table.Step 9: Run the simulation again and record your data.Use X for "die out," for "increase in numbers," and for "decrease in numbers."

(X, , or )

Plant Plant Plant Herbivor

ABCeA

HerbivoreB

HerbivoreC

OmnivoreA

OmnivoreB

TopPredator

Simulation 1

Simulation 2

Answer the following:

1.

Was your prediction correct? How did you arrive at your prediction? What differences were therebetween your prediction and the simulation?

Our prediction was correct and no different between the prediction and the simulation. We predicted thatbecause we observed from the food web.

Part III: Removing the Predator

Step 1: Reset simulation.Step 2: Click on All off icon.Step 3: Click on all the plant icons. They plants should cover up the bare ground on simulation.Step 4: Click on Herbivore A. Select Herbivore A eats Plant A and B. Click on Herbivore B. Select Herbivoreeats Plant A and C. Click on Herbivore C. Select Herbivore eats Plant A, B, and Plant C.Step 5: Click on omnivore A. Select omnivore A eats Plant A and B. Click on omnivore B. Select omnivore Beats herbivore A and B, and Omnivore A.Step 6: Top Predator has gone extinct and should not be clicked.

Prediction: Population of omnivoreB, herbivoreB and herbivoreC will increase because no others animal eatthem. By the way, herbivoreA will decrease.

Step 7: Click on the Run icon. The simulation will run for 100 days.Step 8: Record your results in the Data Table.Step 9: Run the simulation again and record your data.Step 10: Run simulation until the populations become stable.Use X for die out, for increase in numbers, and for decrease in numbers.(X, , or )

Plant Plant Plant Herbivor

ABCeA

HerbivoreB

HerbivoreC

OmnivoreA

OmnivoreB

TopPredator

Simulation 1

Simulation 2

Answer the following:

1.

Was your prediction correct? What differences were there between your prediction and the simulation?

At first, we predicted that population of omnivoreB, herbivoreB and herbivoreC will increase butpopulation of herbivoreA will decrease so only prediction of herbivoreC and herbivoreA is correct. Ourprediction are population of omnivoreB and herbivoreB will increase but their population are both decrease.2.

What was the effect of the top predator on the ecosystem?

The ecosystem is not balance because there arent any predator eating the omnivore then they will beincreased and the more population the more food they need so this lead to extinction of plants.3.

What effect did removing the predator have on the ecosystem?

When the top predator gone, omnivore and herbivore will be increased but plants will be decreasedbecause too many herbivore and omnivore eating them.4.

Was the ecosystem with or without the top predator most stable?

The ecosystem without the top predator is the most stable one as the virtual lab had shown above. Onthe last one where theres no top predator the graph is stable since day 50-60.5.

Which organism in this simulation was the keystone species?

We believe that the Omnivore B was the keystone species in this simulation because if they becomeextinct other animal may not be able to survive. When they die no one would consume Omnivore A and also theHerbivore A. This will allow those species to increase their population and when the population is increase thenthe producer will become lesser and later extinct. When they become extinct the Omnivore A would not have

nothing to consume. The the Herbivore A will be competing with the Herbivore B for food and Herbivore Bwill be competing with the Herbivore C for food then the producer will not be able to reproduce in time.6.

How long did it take for the ecosystem to become stable after the removal of the top predator?

Not for a long time for the ecosystem to become stable after the removal of the top predator. As thedata is shown below it took less than 37 days for the ecosystem to become stable again after the removal of thetop predator.